Was the "second world" a political or a geographical notion? What of the nebulous notion of "the Americas," does this category denote a physical place or an ideological space? The intersection of these two questions almost brought the world to the brink of nuclear warfare in October 1962. The most confrontational episode of the Cold War, in other words, was caused by the liminal place of Cuba within two competing regional imaginaries: the "Americas" vis-à-vis the "Second World." This article revisits the famous Cuban Missile Crisis to reflect on the persistence of legalised spheres of influence in international legal thought and practice. I argue that the institutional structure of regional organisations, and the Organisation of American States in particular, played a pivotal role in how each superpower approached the making and policing of the geopolitical boundaries of each of the "three Worlds" – with consequences that long exceed the Cold War.